The present disclosure relates to a speed change device.
A speed change device that includes a multi-plate friction-type hydraulic clutch is known. The multi-plate friction-type hydraulic clutch has, for example: a plurality of friction plates fitted with splines of a clutch hub so as to be movable in the axial direction; a plurality of separator plates fitted with splines of a clutch drum so as to be movable in the axial direction; and a piston capable of pressing and releasing the friction plates and the separator plates, which are disposed alternately, in the axial direction.
When the piston presses the friction plates and the separator plates, which are disposed alternately, in the axial direction, the friction plates and the separator plates contact each other. That is, the friction plates and the separator plates are frictionally engaged with each other so that rotary elements coupled to the clutch hub and the clutch drum are rotatable together with each other.
When the piston is moved away from the friction plates and the separator plates, which are disposed alternately, on the other hand, the friction plates and the separator plates are released. When the friction plates and the separator plates which have been released are moved away from each other, the rotary elements which are coupled to the clutch hub and the clutch drum rotate relative to each other (idle).
In order to supply lubricating oil that has been supplied into the clutch hub evenly to the friction plates and the separator plates, in addition, oil feed holes formed in oil feed grooves (tooth root portions) of the splines of the clutch hub are formed such that the number of oil feed holes on the clutch piston side is larger than the number of oil feed holes on the end plate side. This prevents occurrence of seizure, accompanying rotation, and poor disengagement due to poor lubrication.